Penis size causing a problem....

Why use coke when lidocaine sprays are around, legal, and not useful for other endeavors?
Was it convenience?

As for dealing with incomparable size, (and my experience is vaginal only, someone with anal experience, please chime in) patience is key. She can't be torquing down, as is instinct, post orgasm helps considerably.

From the guy's perspective, be prepared to stop at any point and continue with other stimuli, for both of you.